This invention relates to anti-tamper closures and it particularly, but not exclusively, relates to closures having tamper evident features for blow-moulded containers.
A known tamper evident container closure comprises a container having a neck in combination with a closure for the container neck, the neck and closure having rotatably interengaging features whereby the closure can removeably close the neck and seal the container and a continuous or segmented tamper evident ring attached by frangible links to the closure, the ring and the container neck having complementary one-way features that, in use, permit closing rotation of the closure and ring relative to the container but which interact to prevent opening rotation of the ring and thereby break the frangible links to provide tamper indication. The closure and tamper evident ring are usually integrally-formed of plastics by injection-moulding and the container necks with the one-way features are either separate plastics mouldings welded or other-wise attached to a container or the container is, preferably, a unitary plastics blow-moulding with all neck features being formed integrally with the container. Such 220 liter (55 gallon) containers are rapidly becoming a standard in many industries, including containers for drink concentrates.
Documents EP-A-0 324 196; U.S. Pat. No. 4,308,969; DE-A-30 10 769; U.S. Pat. No. 4,607,759 disclose examples of this type of tamper evident container closure. There are problems with this type of container closure. One problem is that the closure has to be fitted to the container by relative rotation of the closure with the one-way features riding one over the other until the closure closes and seals the container neck, this exerts a significant closing torque or relative turning force between the closure and the ring and the links have to be strong enough to resist this force. These xe2x80x9cstrong enoughxe2x80x9d links are either too strong for the closure to be readily removable or, more importantly, can permit the closure to be rotated off the container without breaking the links; as the ring can ride backwards over the one-way features without breaking some or all of the links. Another problem is that the fitting of closures to containers is often mechanised and the closing torque set for closure rotation, to ensure a reliable seal between the closure and the neck of a blow-moulded container is often so high that the links can break on driving the closure onto the container neck.
The present invention provides a solution to the above-stated problems.
According to the present invention, a method of fitting a tamper evident container closure to the neck of a container is carried out by:
providing rotatably interengaging features on the container neck and closure by which the closure can removeably close the neck and seal the container;
attaching a continuous or segmented tamper evident ring by frangible links to the closure;
providing complementary one-way features on the ring and the container neck that, in use, permit closing rotation of the closure relative to the container but which interact to prevent opening rotation and thereby break the frangible links;
providing the closure and the tamper evident ring with driving features;
providing a closure fitting tool with driving features complementary to those of the closure and the ring;
loading the fitting tool with a closure;
offering the tool to a container neck; and,
rotating the tool with respect to the container to drive the closure and the ring onto the neck.
By this means, the closure tool effectively bridges the frangible links and exerts closing torque directly on the tamper evident ring as well as on the closure such that the links can be more readily frangible as they do not have to transmit closing torque from the closure to the ring.
It is known to provide a tamper evident container closure with a driven tamper evident ring in the form of a one-way feature depending from the closure and engaging a complementary one-way feature of the ring. Not only is such a closure more difficult to mould than a closure for the method of the present invention but the complementary one-way driving features can make the closure difficult to undo.
In an accordance with the present invention, the complementary tamper evident ring is provided with one-way driving features, to thereby prevent rotation of the tool in the opening direction from driving the tamper evident ring. This prevents a closing tool being used to open a container without breaking the frangible links.